Various uses for continuous loop band saws have evolved in industry, and numerous band saw apparatus have been developed. Band saw apparatus typically comprise a frame with a pair of aligned wheels rotatably mounted to the frame in spaced apart relationship. A continuous loop saw blade is mounted on the wheels and rotated thereby, and two blade guide assemblies are typically mounted to the frame intermediate the wheels. The blade guide assemblies slidingly engage the saw blade to orient it in a generally upright cutting position defining a saw blade cutting stretch intermediate the saw blade guide members. The saw blade and the workpieces are displaced relative to one another so that the saw blade contacts and cuts the workpieces at the saw blade cutting stretch.
The primary goals of band saw apparatus are generally to provide consistently accurate cuts in as many workpieces per unit time as possible, without causing excessive stress on the band saw blade or the saw blade drive means. Common problems with prior art band saw apparatus include deviation of the saw blade and misalignment of the frame during cutting, which result in non-uniform cutting of workpieces and increased saw blade stress and wear. Saw blade fatigue results from bending the continuous loop saw blade around the rotating wheels and from orienting the saw blade in a cutting position along saw blade cutting stretches (usually by twisting the blade by 90. between the drive and idler wheels), and it is therefore desirable to cut as many workpieces as possible per saw blade revolution.
Since the portion of the cycle time devoted to aligning workpieces in a cutting position and clearing cut workpieces from the cutting position remains constant regardless of the number of workpieces being cut, efforts have been directed to cutting multiple workpieces simultaneously to improve cutting efficiency and reduce saw blade stress and wear. The common problems are exaggerated when multiple workpieces having a relatively small cross-sectional surface area are aligned and cut simultaneously in an attempt to improve cutting efficiency. In general, saw blade deflection increases as a function of the third power of the length of the saw blade cutting stretch and the distance between saw blade guide members increases. For this reason, it is desirable to provide a relatively short saw blade cutting stretch.
One approach which has been taken to attempt to increase band saw cycling efficiency when cutting small diameter workpieces, such as dowels, bars and the like, has been to bundle or group multiple workpieces together for simultaneous cutting. Multiple workpieces having relatively small diameters, when bundled together, however, easily become misaligned during cutting at a single saw blade cutting stretch, and complex vise assemblies may be required to position and hold the workpieces during cutting. Moreover, since the saw blade must pass through several side-by-side bars without clearing of metal chips from the gullets of the blade, the blade speed must be lowered to approximately the same speed as if a single large diameter workpiece was being cut. Still further as the bundle size increases, the blade guides must be separated, and blade deflection as a result of separation rapidly increases.
One approach to the problem of saw blade deflection between the saw guide assemblies is shown in U.S. Pat. No. 3,789,717. This patent teaches a band saw apparatus having three blade guide members spaced apart from one another defining a single saw blade cutting stretch between the outer blade guide members. The intermediate blade guide member is centrally positioned between the outer blade guide members and is freely movable away from the blade in a direction substantially parallel to the plane of the saw blade cutting stretch. The intermediate blade guide member contacts the saw blade to provide additional support prior to cutting and during entry of the saw blade into the workpiece. The central guide assembly is lifted away as the saw blade enters the workpiece. The band saw apparatus taught by the '717 patent provides a single saw blade cutting stretch between the outer blade guide members, and it does not overcome the deficiencies of prior art band saw apparatus pointed out above with respect to cutting a plurality of aligned workpieces simultaneously once the blade has entered the bundle of workpieces.
Accordingly, it is an object of the present invention to provide a band saw apparatus and method for accurately and uniformly cutting multiple workpieces simultaneously.
It is another object of the present invention to provide a band saw apparatus providing enhanced band saw cutting efficiency.
It is yet another object of the present invention to provide a band saw apparatus for cutting multiple workpieces simultaneously at each of a plurality of band saw cutting stretches.
It is still another object of the present invention to provide an improved method for aligning and cutting multiple workpieces simultaneously with a band saw apparatus.
A further object of the present invention is to provide a band saw suitable for simultaneous cutting of multiple workpieces with minimum blade fatigue.
Another object of the present invention is to provide a band saw guide assembly for guiding the band saw blade which is durable, can be retrofit to existing saws, requires minimum maintenance and is inexpensive to construct.